This is not about redirecting /index.php?id=6252 to /category-name.

It's about redirecting:

/category-name?ref=blabla&something=useless-stuff
/category-name?
/category-name????????

to:

/category-name

in a small website that does not use GET methods at all.

I have never seen this technique used (or discussed) anywhere, even Google allows you to visit:

https://www.google.com/????? (PR=0)

instead of:

https://www.google.com/ (PR=9)

I don't like adding extra HTML tags (i.e. canonical) or HTTP headers to my website, so I thought why not this?

My biggest fears though is that search engines wouldn't appreciate it.

I just came to this question but it doesn't add much, I'm not planning to share URLs with extra parameters: Google adds useless parameters to my URL

Update: I'm starting to believe there's nothing wrong with this technique.

Videos from Matt Cutts:

• What are the advantages of 301 redirects over rel="canonical"?
• Is there an advantage to using rel="canonical" over a 301 redirect?

And an image picked from a moz article (look at that ?ref=123 example!):